We've had two recent Ricin mailings, the second to the white house, by a guy claiming to own a trucking company who is upset about regulations restricting the hours a driver can drive.
I think his point is that we cannot afford to assume that these attacks are purely domestic. And just because the mailing is domestic, doesn't mean that the actual source is too. Even some Americans can be bought.
Boy, the irony is rich on this one.
Anyone posting "we cannot afford to assume this attack was from Muslim terrorists" in regard to the Anthrax mailings, despite the letters connected to the attacks, they'd get flamed viciously.